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What can be done is to take thousands of people, ask them how much milk they have drank in recent years and then follow them up for at least a decade to see if those who drink milk regularly are less likely to break bones along the way. following years.

This is what happened in a study published in 1997 by Harvard University.

For 10 years, they followed 77,000 nurses.

And the researchers found no significant difference in the number of arm or hip fractures between those who drank a glass of milk per week or less and those who drank two or more glasses.

The team conducted a similar study with 330,000 male health professionals, and once again the milk did not seem to influence the fractures.

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Image caption Many studies analyze the relationship between milk consumption and bone fractures.

There are also records of other randomized controlled trials in which scientists deliberately fortified the diet with calcium, sometimes through milk.

In 2015, a team from New Zealand reviewed, compared and reanalyzed 15 of these studies.

And they discovered that for two years there was an increase in the bone mineral density of the participants, but after that time the improvement stopped .

An alternative to milk is to take calcium supplements. Concerned about the potential long-term side effects of taking the supplements, the same New Zealand team analyzed the data from 51 randomized controlled trials to assess whether the benefits outweighed the risks.

Again, they discovered that the increase in bone strength lasted only a year or two, and that calcium supplements alone could slow-and not stop-the loss of bone mineral density in old age.

They concluded that this probably translated only into a small reduction in bone fractures .

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Image caption The United States recommends drinking three glasses of milk a day, almost double that of the United Kingdom or India.

Several countries examined the same data, but reached very different conclusions about the recommended daily calcium intake .

The US, for example, recommends drinking three glasses of milk a day, almost twice as much as the United Kingdom or India.

To complicate things further, in 2014 the results of two large Swedish studies were published.

The headlines about the studies claimed that drinking more than three glasses of milk a day, an amount greater than most people drink, was not good for the bones and could even be harmful .

These studies were carried out by a team of researchers from the University of Uppsala and the Karolinska Institute, both in Sweden.

Participants had to fill out questionnaires about their milk consumption in 1987 and then do the same in 1997.

In 2010 they analyzed their mortality rates , and alarms went off among the population when it was revealed that drinking a glass of milk a day seemed to be associated with more broken bones and, also, with early deaths.

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Image caption It’s hard to know how much milk we drink with cereals or tea, for example.

But before giving up milk forever, you have to make some important warnings.

In the Swedish studies, the participants had to estimate their milk consumption during the previous years, which is not easy.

It’s hard to know how much milk we drink with cereals or tea or how much we use for cooking.

In addition, the studies also show the eternal problem of correlation versus causality .

Perhaps women who knew they had osteoporosis drank more milk deliberately in the hope of strengthening their bones.

The study did not show that drinking milk caused the fractures.

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Image caption Vitamin D also contributes to strong bones.

And there is more: the Swedish team discovered that consumption of cheese and yogurt was associated with lower fracture rates.

The researchers themselves made it clear that their studies should be repeated before they were used to give dietary recommendations.

It was also said that people should think twice before modifying their milk consumption based on these results.

So, until we know more, what the evidence suggests is that nothing happens by continuing to drink milk if you like.

It is likely to be good for bone health, even if the benefits last less than you probably expected.

It is also worth keeping strong bones through other methods, such as exercising and getting enough vitamin D from your diet, from sunlight or (depending on the place in the world you live) from vitamin supplements in winter.